1. Field
Aspects of the present invention relate to a rechargeable battery and a manufacturing method thereof.
2. Description of the Related Art
A rechargeable battery is a power storage system that converts electric energy into chemical energy and stores the same in a high energy density. Unlike primary batteries that are not designed to be recharged, secondary batteries that are rechargeable are widely used in IT devices, such as smart phones, cellular phones, notebook computers, tablet PCs, and so on. In addition, recently, due to an increase in oil prices, electric vehicles are drawing attention and there is an increasing tendency to use rechargeable batteries as power sources for electric vehicles. With such a trend, the secondary batteries need to provide characteristics such as high density, high capacity, high output, stability, and so on.
The rechargeable battery may be largely classified as a lead storage battery, a nickel-cadmium battery, a nickel hydrogen battery, a lithium ion battery, a lithium polymer battery, and so on. Among others, lithium ion batteries or lithium polymer batteries are rapidly being applied to portable IT devices owing to their advantages, including high operating voltages, high energy densities per unit weight, and so on.
Among various components of a rechargeable battery, an electrode plate should be cut accurately and adequately according to the size of a rechargeable battery to be manufactured to increase the capacity while reducing capacity dispersion, thereby increasing the quality of the rechargeable battery. In order to accurately cut the electrode plate, cutting or severing is generally performed using a mold.
However, frequent maintenance and repair of the mold should be done due to the limited life span of the mold, and the mold may be replaced according to a change in the product specification. Due to the frequent maintenance, repair and replacement of the mold, facility maintenance costs may be relatively high and the production quality may be low. In addition, from the viewpoint of quality, cutting quality may deteriorate as a cutting blade becomes blunt with repeated uses of the mold, so that a sharp burr may occur on the electrode plate. Therefore, repeatedly cutting electrode plates using the mold may make it difficult to maintain uniformity in cutting quality.
In particular, the likelihood that the burr would occur on the electrode plate depends highly on the state of mold used and mold setting clearance. A sharp burr of approximately (about) 15 μm or greater may pierce a separator having a thickness in a range of approximately (about) 20 μm to approximately (about) 30 μm, thus separating electrode plates from each other and resulting in an electric short between the electrode plates. In addition, since the burr is apt to be stripped off even by a slight shock, it may function as a metallic foreign material in a battery, thereby considerably degrading the quality of a rechargeable battery or battery cell.